Machines often use linkages to support work implements for digging, lifting, clearing, or smoothing. Examples of these machines include excavators, loaders, dozers, motor graders, and other types of heavy machinery. These linkages are typically controlled by an operator input device, and often include monitoring of the position of the linkage and the work implement. These machines can be controlled by an operator in the machine, controlled remotely by an operator, or controlled through automation.
For example, an operator input device such as a joystick, a pedal, or any other suitable operator input device may be movable to generate a signal indicative of a desired velocity of an associated linkage and work implement. When an operator moves the operator input device, the operator expects the linkage and work implement to move through its free range of motions. However, in some implementations, the free range of motion is not available. The free range of motion is not available because of the risk of colliding with other parts of the machine or other linkages, or zones of movement where position data is unreliable. Attempts to avoid these risks by restricting the range of movement of the linkage and work implement often result in the operator losing more than the minimum range of motion necessary to avoid these risks.
One method of improving the utilization of the range of motion of a linkage while avoiding collisions with other linkages is described in U.S. Pat. No. 6,819,993 (the '993 patent) issued to Koch on Nov. 16, 2004. The '993 patent describes a system and method for estimating the position of a mechanical linkage of a machine. The estimated position of a mechanical linkage is set to an initial position. The estimated position of the mechanical linkage is updated based upon the movements of the mechanical linkage. A determination is made when the estimated position of the mechanical linkage substantially corresponds to an actual position of the mechanical linkage. The estimated position zone of the mechanical linkage is used to prevent collisions with other mechanical linkages.
Although the system of the '993 patent may reduce collisions and damages to, and between, linkages, the system of the '993 patent does not allow movement of other linkages through zones where the position data is unreliable. For example, a soft fault of the wiring harness may make the position data unreliable, and the system of the '993 patent does not allow the mechanical linkages to be operated safely when both their positions cannot be determined or estimated.
The disclosed linkage control system is directed to overcoming one or more of the problems set forth above.